1. Field of the Invention
The present invention relates to a venting apparatus for a tire vulcanizing mold, and in particular to a venting apparatus for a tire vulcanizing mold which is capable of enhancing a discharging capacity of air by improving a venting apparatus installed in a vulcanizing mold, preventing a vent rubber formed when a rubber flows into a venting apparatus from being formed in a finished tire, preventing an error operation during a vulcanization, extending a life span of a venting apparatus and implementing an easier maintenance.
2. Description of the Background Art
Generally, a green tire which is a fabricated in a raw rubber state is a tire vulcanized in a vulcanization mold of a high temperature and pressure. A vulcanization mold is formed of a mold segment and a bladder which pressurizes a green tire in a mold. A vent hole is installed in an inner side surface of a mold for discharging air from a portion between a green tire and a mold to the outside.
The above vent hole is formed to discharge air as well as a rubber of a green tire based on a vulcanization pressure. Since the finally fabricated tire has a vent rubber on the surface of the same, a trimming process should be performed for removing a vent rubber.
In order to overcome the above problems, FIG. 1 is a view illustrating a venting apparatus (DE 195 43 276 C1) which is one of the conventional venting apparatuses.
As shown in FIG. 1, the venting apparatus includes a casing 14 inserted in a vent hole 12 of a mold 10, a valve body 18 inserted in a center through hole 16 of the casing 14, a spring (pressure or return spring) 20 elastically installed in the valve body 18, and a stopper 22 which is engaged to a lower end portion of the valve body 18 and controls a moving distance in a vertical direction of the valve body 18.
In addition, the valve body 18 includes a valve insert 24 which is provided in the center through hole 16 of the casing 14 and is surrounded by the spring 20, and a valve head 28 which contacts with a slant surface formed in an upper portion of the center through hole 16. Here, the side surface of the valve head 28 has a slant surface 30 having the same slant angle as the slant angle of the slant surface 26 formed in the upper portion of the center through hole 16. Two slant surfaces 26 and 30 surface-contact each other, and the alternate interior angles of two slant surfaces are same.
In the above venting apparatus, since the slant angles of the slant surface 30 of the valve head 26 and the slant angle of the upper slant surface 26 of the center through hole 16 are same, when a rubber flowing through a portion between the slant surfaces 26 and 30 blocks the gaps for a short time, an air discharging capacity of the venting apparatus is decreased. In other words, even when a small gap is provided, the rubber of the green tire may penetrate into the gap by a high pressure during the vulcanization.
In addition, in the case that the rubber is held in one of the left and right slant surfaces 26 and 30, the valve head 28 may be eccentric, so that the vent rubber may be formed in the vulcanized tire.
The outer circumferential portion of the casing 14 is formed in a cylindrical shape and has the same diameter in its whole portions. The inner portion of the vent hole 12 of the mold 10 into which the casing 14 is inserted, is formed in a cylindrical shape. In the case that the inner diameter of the vent hole 12 is the same as the outer diameter of the casing 14, since the casing 14 is supported by only friction force with the inner circumferential portion of the vent hole 12, the casing 14 may be pushed into the interior of the vent hole 12 by a high pressure during the vulcanization.
In addition, since the diameters of the upper and lower portions of the center through hole 16 formed in the center of the casing 14 are same, and the diameters of the upper and lower portions of the valve insert 24 are same, the inner volume of the center through hole 16 is always same in its upper and lower portion. Therefore, the space between the inner surfaces of the valve insert 24 and the center through hole 16 are very small, and the space in their upper and lower portions are same, in the case that the rubber which flows into the interior of the center through hole 16 is held between the spring 20, an elastic moving capacity of the valve body 18 may be lost, so that the venting apparatus may no be operated.